Unveiling unconventional magnetism at the surface of Sr2RuO4
R. Fittipaldi, Roman Hartmann, Maria Teresa Mercaldo, Sachio Komori, Anders V. Bjørlig, Wonshik Kyung, Y. Yasui, Takushi Miyoshi, L. A. B. Olde Olthof, Carla M. Palomares García, V. Granata, Itai Keren, Wataru Higemoto, Andreas Suter, Thomas Prokscha, Alfonso Romano, Canio Noce, Changyoung Kim, Y. Maeno, Elke Scheer, Beena Kalisky, Jason W. A. Robinson, Mario Cuoco, Z. Salman, A. Vecchione, Angelo Di Bernardo
Abstract
Abstract Materials with strongly correlated electrons often exhibit interesting physical properties. An example of these materials is the layered oxide perovskite Sr 2 RuO 4 , which has been intensively investigated due to its unusual properties. Whilst the debate on the symmetry of the superconducting state in Sr 2 RuO 4 is still ongoing, a deeper understanding of the Sr 2 RuO 4 normal state appears crucial as this is the background in which electron pairing occurs. Here, by using low-energy muon spin spectroscopy we discover the existence of surface magnetism in Sr 2 RuO 4 in its normal state. We detect static weak dipolar fields yet manifesting at an onset temperature higher than 50 K. We ascribe this unconventional magnetism to orbital loop currents forming at the reconstructed Sr 2 RuO 4 surface. Our observations set a reference for the discovery of the same magnetic phase in other materials and unveil an electronic ordering mechanism that can influence electron pairing with broken time reversal symmetry.